1. Field of the Invention
The present invention generally relates to a cable connector for balanced transmission in which a number of pairs of wires are used.
2. Description of the Related Art
As data transmission systems, there are systems such as a normal transmission system that uses a wire for each data signal, and a balanced transmission system that uses a pair of wires for each data signal and transmits a + signal and a − signal, whose size is the same as that of the + signal with the opposite direction from the + signal, at the same time. The balanced transmission system has an advantage of being relatively immune to noise compared with the normal transmission system. Therefore, the balanced transmission system has been widely used. In order to establish a transmission line that executes balanced transmission of data between apparatuses, a cable connector for balanced transmission is used. The cable connector for balanced transmission is shielded at the end of the cable for balanced transmission.
FIG. 1 is an exploded perspective view of a conventional cable connector for balanced transmission 10. FIG. 2 is a cross-sectional view of the conventional cable connector for balanced transmission 10 shown in FIG. 1. In drawings, a line X1–X2 shows the width direction, a line Y1–Y2 shows the length direction, and a line Z1–Z2 shows the height direction.
FIG. 3 is a cross-sectional view of a cable for balanced transmission 20 shown in FIG. 1. As shown in FIG. 3, the cable for balanced transmission 20 has a structure in which a number of pairs of wires 21 are disposed in a tube of a double-cover tube composed of an outer cover 27 and a shielding mesh wire 28, where each of the wires 21 has a pair of first and second covered signal wires 22-1 and 22-2 for balanced signal transmission and a drain wire 25 banded by a spirally-wrapped metal tape. As shown in FIG. 6, from the end of the pair of wires 21, the first and second covered signal wires 22-1 and 22-2 and the drain wire 25 are extended, and the covers at the tips of the first and second covered signal wires 22-1 and 22-2 are removed and first and second signal wires 23-1 and 23-2, respectively, (tips of the first and second covered signal wires 22-1 and 22-2) are naked and exposed. The first signal wire 23-1 pairs up with the second signal wire 23-2.
As shown in FIGS. 1 and 2, in the cable connector for balanced transmission 10, a relay board 12 is provided at the Y1 side of a contact assembly body 11, and the first and second signal wires 23-1 and 23-2 and the drain wire 25 further extending from the pairs of wires 21 extended from the end of the cable for balanced transmission 20 are soldered to terminals of the Y1 side of-the relay board 12. In addition, shielding covers 31 and 32 cover the contact assembly body 11, the relay board 12, and the end part of the cable for balanced transmission 20. In the cable connector for balanced transmission 10, the contact assembly body 11, the relay board 12, and the ends of the cable for balanced transmission 20 form data transmission paths (refer to Patent Document 1).
[Patent Document 1] Japanese Laid-Open Patent Application No. 2003-059593
In the cable connector for balanced transmission 10, when the shield between the adjacent two data transmission paths is studied, there is a problem in the part of the relay board 12. That is, the relay board 12 has a structure in which wiring patterns extending in the Y1–Y2 direction are formed on the upper face and the lower face of the relay board 12 in a manner so that the wiring patterns are arrayed in the X1–X2 direction, and the wiring pattern on the upper face pairs up with the wiring pattern on the lower face at the same position. Consequently, it is difficult to provide excellent shielding at the place between adjacent wiring patterns in the X1–X2 direction comparable to the shielding degree at the contact assembly body 11.
Recently, the signal speeds in clients and servers have become high; therefore, a bad influence on transmission characteristics caused by poor shielding at the relay board 12 cannot be ignored.
In addition, a cable connector for balanced transmission is required for which low cost manufacturing and highly efficient assembly can be achieved.